From the email you've received, tap on the 'Read my message' button:
To keep things secure, we'll send you a 6 digit code you'll use to open your message. Tap on 'Send code' :
You'll be taken to a screen to enter the code, but first we need to get it. You may be able to copy it from a notification you receive, but if you don't see one, tap on the back arrow at the top left of the screen:
This will return you to the message you received. Tap on the back button at the top left again.
You're taken to your inbox. Wait for a new email to arrive with a secure email verification code. You may be able to see the code from this screen, but if not, tap on the message to open it:
Make a note of the 6 digit code, then tap on the back button at the top left to return to your inbox.
From there, return to the original email you received and tap on 'Read my message' again. This will return you to the code screen. Enter the 6 digit code you got in the last step:
Tap on 'Verify code' and you'll be through to your message:
Any attachments on the email can be opened/downloaded by tapping on them.